Mechanical Head Question

[Darkness_is_spreading]

I'm wondering if a 85 mechanical head would fit onto a hydraulic bottom end TD 86-92.  

Also I was wondering how high these diesels can rev when preperly lightened; flywheel, Windage tray, profiled and balanced crank.....  Then with the addition of the mechanical head, you would have alot less problems with high rev's because of the solid lifters.

I was told that these motors (hydraulic) grenade at 7000 rpm I believe this is cause by the slapping of valves because the hydraulic valves are adjusted by the pressure of the motor.  

So I was thinking of mating a 90 TD block with an 85 mechaical head lightening what I could, K26 turbo, pump, IC, exhaust and seeing if it would be awesome

[935racer]

I'll some it up real quick for you, absolutely pointless.


The motors themselves can rev to 7000 rpm, but you would have crazy valve float, and not just from hyd lifters, but from the boost pressure you would likely be runnign at that rpm, with the size of turbo you could run at that rpm would increase your peak cylinder pressures to the point that your valves would never seat.
\
\The major issue here is the fuel, and more specifically the lack of dynamic advance, while it would be possible to get a 9mm ve pump to rev to 7000rpm, but your injection and ignition lag would be too wide, and you will make no power.

[935racer]

Oh I'll add though, lighten up the bottom end if you get the chance even if tis just a lightweight flywheel, and always balance the bottom end. The balancing  will help smooth out your idle and revving and the lightening makes the engine a little revvier, and most people find that it just really makes the power over a more useable power band.

[rabbid79]

Valve float and injection timing issues aside, what is the fastest a diesel can spin, and still complete the combustion process?

[935racer]

Who knows, it DOES NOT matter if you can't advance the dynamic timing enough to keep your IGNITION and INJECTION lag in check.

[rabbid79]

Not to beat a dead horse, but this issue of dynamic timing you're referring to... this is injection timing in relation to crank angle right?  I understand that there's only so much fuel timing advance you can eek out of a fuel injection pump.  So if that's the limitation, would there be any advantage to installing one of these in place of the stock pump gear? http://forums.vwvortex.com/zerothread?id=2704589

[935racer]

Ahhh crap, now you got me on the drawing board. To simply answer the question, as is, no this won't work. As mounted on the engine this gear is 7 degrees statically advanced +7 degrees, by 4000 rpm it is -3 degrees retarded. Now this unit can most definately be modified. I think I could make it work. Like I said to the drawing board...

P.S., thanks for the idea I've never even seen one of those gears before. :shock:

[tylernt]

I thought Malone or Giles or somebody did a governor mod that let them run up to 6000+ RPM? Am I making this up?

And in answer to the other question, you can put a solid head on a hydraulic motor, but you have that extra oil return between cylinders #1 and #2 that you need to seal up so you don't blow crankcase vapors and oil mist everywhere.

[rabbid79]

I'm glad you're looking into this.  It would be cool if it could work.

[935racer]

I thought Malone or Giles or somebody did a governor mod that let them run up to 6000+ RPM? Am I making this up?

And in answer to the other question, you can put a solid head on a hydraulic motor, but you have that extra oil return between cylinders #1 and #2 that you need to seal up so you don't blow crankcase vapors and oil mist everywhere.

Yes governor mods are quite common, I do a few a month for customers, and while you can rev to 6k+ it doesnt give you the extra dynamic timing advance necessary to make power up there. And you can actually increase the dynamic advance by modifying the timing piston inside the pump, but eventhis is quite limiting and does not give you enough advance to make power up to and beyond 6 grand.

[Benjamin]

Dynamic timing

The maximum angle is 12degrees camshaft (24degrees crankshaft)

this is what a Bosch VE pumps manual is saying.

how can we know we are on 12degrees, please dont say to try out  

Greetz, Benjamin

[935racer]

Dynamic timing

The maximum angle is 12degrees camshaft (24degrees crankshaft)

this is what a Bosch VE pumps manual is saying.

how can we know we are on 12degrees, please dont say to try out  

Greetz, Benjamin

Sorry I don't really understand what you are asking, can you rephrase what you would like to know?

[gldgti]

interesting thread....

someone asked "how fast can a diesel spin?"

its an interesting topic, and one which i actually hope to investigate professionally one day?

explain? right.

the critical thing is the speed of combustion. direct injection diesels have a slow combustion cycle which peaks its effective power producing capabilities around the upper rev range of most "ultra modern" high performance diesels - ie about 5000rpm.

we are lucky. IDI combusion process is infact significantly faster and it is an area of underfunded development that needs to be investigated more if diesel technology is to keep evolving.

i am personally of the mind that research into pre-combustion chamber design is where further development will occur...so what am i saying?

if we can do all the important stuff - keeping the valves in check, keeping the pump timing up to the correct stage and make sure we have enough boost to get all the fuel to explode - theres no reason we cant make diesels to go very...very fast. 9000rpm? sure.

someone help me out!

[rabbid79]

Hi, I'm not sure what kind of "help" you need, but I too am VERY interested in just how fast I can spin my engine.  I'm working on a VNT 1.5 project.  My philosophy behind making HP is to keep the peak torque down and the revs up.  I'm not going to say in public how much HP I'm looking for, but just to give you an idea, I've got a 2.25" exhaust, a VNT-17, and a K&N with 60 square inches of surface area.  I'm looking to keep the torque under 125 ft./lbs.  To reach my HP goal, I need to spin the motor to at least 6000 RPM.

I'm sure as my project progresses from bone stock through the initial stages of turbocharging, it won't take long to find the engine's weaknesses.  I figure the head gasket will go first.  Once it does, it's a perfect excuse to modify the head.  I'd like to shape the intake ports to 'D' ports so I can use a TDI manifold, lighten the valve train, install TD exhaust valves, thermal coat the precups and the exhaust ports, install variable cam gears on the cam and the fuel pump (if possible), install ARP head studs, and throw on a G60 valve cover.

Let me know what kind of "help" you need.